Note: Descriptions are shown in the official language in which they were submitted.
CA 02407506 2002-10-24
WO O1/83932 1 PCT/GBO1/01512
1 Expandable Apparatus for Drift and Reaming a Borehole
2
3 This invention relates to an expandable reamer shoe which
4 can be used to drift and ream drilled well bores, as are
typically used in oil and gas production.
6
7 When constructing a well bore, it is standard practice to
8 drill in intervals. Firstly, a large surface hole is
9 created into which casing is installed to act as a lining
in the bore. Cement can then be displaced between the
11 external surface of the casing and the interior of the
12 well bore in order to structurally support the casing.
13 In order to drill the next and deeper section of the bore
14 it is common practice to use a smaller drill bit attached
to a drill string which can be lowered through the
16 previously installed casing in the first section of the
17 bore. Consequently, the next section of the bore, and
18 the casing installed within it, has a smaller diameter to
19 that which is above it. Further sections of well are
then lined with a length of even smaller casing which
21 runs back to the surface and is inserted into the bore by
22 the above described method. Several sections of hole may
23 be drilled before the final back to surface section, near
CA 02407506 2002-10-24
WO 01/83932 2 PCT/GB01/01512
1 the production zone, is drilled and lined with liner,
2 which is hung inside the bore on the last string of
3 casing, rather than being run back to the surface like
4 the casing sections above it.
6 There have been a number of methods recently described
7 whereby steel casing (US Patent No 5667011 and WO
8 93/25799) can be expanded after it has been run into a
9 bore. Expandable casing overcomes the problem inherent
to conventional casing whereby as a consequence of the
11 normal installation procedure, the diameter of the
12 sections of casing decreases with depth in the well-bore.
13 However, if the well bore is not at the planned diameter
14 when the casing is expanded in the hole which may occur
for example, due to hole contraction after the drilling
16 run, there is a danger that the next string of casing
17 when expanded, will not go out to the full size, due to
18 the restricted hole diameter outside the casing.
19
When requiring to drill a hole below the casing, of a
21 size larger than the bore of the casing, it is standard
22 practice to use a drill string with an underreamer and
23 pilot bit. Underreamers are comprised of a plurality of
24 expandable arms which can move between a closed position
and an open position. The underreamer can be passed
26 through the casing, behind the pilot bit when the
27 underreamer is closed. After passing through the casing
28 the underreamer can be opened in order to enlarge the
29 hole below the casing. It is not feasible when running
expanded casing, to drill down the casing using an
31 underreamer attached, as underreamers are not drillable,
32 that is they can only be used when there is a certainty
33 that further sections of the bore will not be drilled, as
CA 02407506 2002-10-24
WO 01/83932 3 PCT/GB01/01512
1 the subsequent drill bit or casing drill shoe would have
2 to pass through the underreamer in order to advance.
3 This is extremely difficult as underreamers are required
4 to ream and remove hard rock material and typically
comprise hard, resilient materials such as Tungsten
6 Carbide or steel. Drilling through an in-place
7 underreamer may result in damaging the drill bit or the
8 casing drill shoe, adversely affecting the efficiency of
9 any further drilling.
11 Other methods include the use of an expandable bit,
12 rather than an underreamer with a pilot solid crown bit,
13 and also a bi-centre bit.
14
It is therefore recognised in the present invention that
16 it would be advantageous to provide a reamer shoe which
17 can be used in conjunction with expandable casing and
18 which is itself expandable, and can drift and ream a
19 drilled section prior to expansion of the casing.
21 It is an object of the present invention to provide an
22 expandable reamer shoe which can be attached to casing
23 and which can drift and/or ream a previously drilled hole
24 regardless of whether the casing is being advanced by
rotation and/or reciprocation of the reamer shoe.
26
27 It is further object of the present invention to provide
28 an expandable reamer shoe which can be used with either
29 expandable casing or standard casing when desired.
31 It is a yet further object of the present invention to
32 provide an expandable reamer which is constructed from a
33 material which allows a casing drill shoe or drill bit to
CA 02407506 2002-10-24
WO 01/83932 4 PCT/GBO1/01512
1 drill through it such that the drill shoe or drill bit is
2 not damaged and can progress beyond the point reached by
3 the expandable reamer shoe within the well bore.
4
According to a first aspect of the present invention
6 there is provided a reamer shoe for mounting on a casing
7 string, the reamer shoe having a plurality of reaming
8 members wherein said reamer shoe is constructed from a
9 relatively soft drillable material, wherein the plurality
of reaming members are moveable between a first and
11 second position, and wherein the reaming members are
12 closed in the first position and expanded in the second
13 position.
14
Optionally the expandable reamer shoe can act as a drift.
16
17 Preferably the plurality of reaming members are in the
18 form of blades.
19
Optionally each of the blades has a hard facing applied
21 to the outer surface.
22
23 In one embodiment, the reaming members move from the
24 first closed position to the second expanded position by
virtue of the movement of an activating piston.
26
27 Most preferably said activating piston defines an
28 internal bore.
29
Preferably movement of the activating piston is provided
31 by an increase in hydrostatic pressure.
32
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WO 01/83932 5 PCT/GB01/01512
1 Preferably the increase in hydrostatic pressure is
2 provided by an obstructing means within the internal bore
3 of the activating piston.
4
Most preferably said obstructing means is a deformable
6 ball or dart.
7
8 Preferably the reaming members are fully expanded when
9 the ball communicates with a seat formation in the
internal bore.
11
12 Preferably the ball is held inside the bore of the
13 activating piston by a retainer ring.
14
Preferably the retainer ring has a plurality of by-pass
16 ports which allow fluid and mud to pass through the
17 retainer ring.
18
19 Optionally the activating piston or retainer ring is
adapted to receive a retrieval tool such as a spear or
21 overshot.
22
23 Preferably the activating piston has an external split
24 ring mounted around the outside diameter.
26 Preferably the split ring can communicate with a groove
27 in the body of the reamer shoe, wherein the activating
28 piston is prevented from moving when the split ring is in
29 communication with said groove.
31 Preferably a plurality of ramps are located externally to
32 the activating piston.
33
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WO 01/83932 6 PCT/GBO1/01512
1 Preferably the activating piston ramp segments, split
2 ring, ball, retainer ring and float valve are drillable.
3
4 In a second embodiment concept of the present invention,
the reaming members move from the first closed position
6 to the second expanded position by virtue of a
7 hydrodynamic pressure drop between the interior and
8 exterior of the reamer shoe.
9
Most preferably said hydrodynamic pressure drop is
11 created by one or more nozzles which may be attached to
12 the lowermost end of the reamer shoe.
13
14 Preferably the reaming members are held in the first
closed position by a plurality of leaf springs.
16
17 Preferably in the second expanded position the reaming
18 members are locked in position by a first and second
19 retaining block at either end.
21 Optionally the reamer shoe may contain a rupture means
22 such as a burst disc, wherein upon rupturing, the rupture
23 means permits the flow area of fluid from the interior of
24 the reamer shoe to the exterior to be increased for ease
of passage of cement, when cementing the casing, after
26 reaming to bottom.
27
28 Optionally the expandable reamer shoe may have a
29 cementing float valve fitted in the nose or the bore of
the body.
31
CA 02407506 2006-04-11
7
According to a second aspect of the present invention
there is provided a method of inserting expandable casing
into a borehole, comprising the steps of;
a) running a first section of expandable casing into a
pre-drilled borehole, expanding and then cementing
(if required) the expandable casing in place,
b) underrearning under the in-place casing using a
standard underreamer and pilot bit or an expandable
bit or bi-centre bit,
c) running a second length of expandable casing through
the in-place casing with an expandable reamer shoe
to ream down by rotation and/or reciprocation to
guarantee the hole is at the expected size
d) After reaming down, if needed, the expandable casing
can be expanded and then cemented (if required) to
create a slimhole or even a mono-bore well. The
expandable reamer shoe, as well as having expandable
blades, can also be designed to have its body
expanded in the same manner as the casing-above it.
The method may further comprise the step of running a
subsequent section of casing through the in-place section
of expandable casing after drilling through the apparatus
of the first aspect to create a new hole or even to use a
casing drill shoe to drill out the nose of the expandable
reamer shoe for drilling and casing simultaneously.
CA 02407506 2006-04-11
7a
According to an aspect of the present invention there is
provided an expandable reamer shoe for mounting on a casing
string, comprising a body upon which are arranged a
plurality of reaming members, wherein the reamer shoe is
substantially constructed from a relatively soft drillable
material, the plurality of reaming members are movable
between a first and second position, the reaming members
are closed in a first position and expanded in a second
position, the reaming members are operable in the second
position to remove a portion of a wellbore, wherein the
reaming members move from the first position to the second
position by virtue of an activating piston, and each of the
reaming members has a hardened material applied to an outer
surface.
According to another aspect of the present invention there
is provided a method of inserting expandable casing into a
borehole, the method comprising the steps of (a) running a
first section of expandable casing into a pre-drilled
borehole, (b) expanding the first section of expandable
casing in place,(c) underreaming under the in-place first
section of expanded casing using a standard underreamer and
bit, (d) running a second section of expandable casing
through the first section of expandable casing with an
expandable reamer shoe, (e) reaming down the borehole by
rotation and/or reciprocation of the expandable reamer shoe
to an expected size, and (f) drilling through the
expandable reamer shoe prior to running a subsequent
section of expandable casing through an in-place section of
expandable casing.
According to a further aspect of the present invention
there is provided a reamer shoe for mounting on a casing
CA 02407506 2006-04-11
7b
string, comprising one or more reaming members disposed on
the body, radially movable from a retracted position to an
extended position, and actuatable to remove a portion of
the welibore, and a locking member made from a drillable
material and which locks the one or more reaming members in
the extended position.
According to a further aspect of the present invention
there is provided a method of inserting casing into a
borehole, the method comprising running a first casing into
the borehole, running a second casing having an expandable
reamer made from a drillable material into the borehole,
expanding the expandable reamer, underreaming an uncased
portion of the borehole using the expandable reamer, and
coupling the second casing to the first casing.
According to a further aspect of the present invention
there is provided an expandable reamer shoe for mounting on
a casing string, comprising a body upon which are arranged
a plurality of reaming members, wherein the reamer shoe is
substantially constructed from a relatively soft drillable
material, the plurality of reaming members are movable
between a first position and a second position, the reaming
members are closed in the first position and expanded in
the second position, and in the second expanded position,
the reaming members are locked in position by a first and a
second retaining block at each respective end of each one
of the reaming members.
According to a further aspect of the present invention
there is provided an expandable reamer shoe for mounting on
a casing string, comprising a body upon which are arranged
a plurality of reaming members, wherein the reamer shoe is
CA 02407506 2006-04-11
7c
substantially constructed from a relatively soft drillable
material, the plurality of reaming members are movable
between a first position and a second position, the reaming
members are closed in the first position and expanded in
the second position, the reaming members are operable in
the second position to remove a portion of a wellbore, the
reaming members move from the first closed position to the
second expanded position by virtue of movement of an
activating piston, and the activating piston has an
external split ring mounted around an outside diameter.
According to a further aspect of the present invention
there is provided an expandable reamer shoe for mounting on
a casing string, comprising a body upon which are arranged
a plurality of reaming members, wherein the reamer shoe is
substantially constructed from a relatively soft drillable
material, the plurality of reaming members are movable
between a first position and a second position, the reaming
members are closed in the first position and expanded in
the second position, the reaming members are operable in
the second position to remove a portion of a wellbore, the
reaming members move from the first closed position to the
second expanded position by virtue of movement of an
activating piston, the reaming members move from the first
closed position to the second expanded position by virtue
of a hydrodynamic pressure drop between an interior and
exterior of the reamer shoe, and the hydrodynamic pressure
drop is created by one or more nozzles attached to a
lowermost end of the reamer shoe.
According to a further aspect of the present invention
there is provided an expandable reamer shoe for mounting on
a casing string, comprising a body upon which are arranged
CA 02407506 2006-04-11
7d
a plurality of reaming members, wherein the reamer shoe is
substantially constructed from a relatively soft drillable
material, the plurality of reaming members are movable
between a first and second position, the reaming members
are closed in a first position and expanded in a second
position, the reaming members are operable in the second
position to remove a portion of a welibore, the reaming
members are biased towards the first position.
According to a further aspect of the present invention
there is provided a reamer shoe for mounting on a casing
string, comprising a body, one or more reaming members
disposed on the body, radially movable from a retracted
position to an extended position, wherein the one or more
reaming members are biased towards the retracted position,
and actuatable to remove a portion of the wellbore, and an
actuator for moving the one or more reaming members between
the retracted position and the extended position, and made
from a drillable material.
According to a further aspect of the present invention
there is provided an expandable reamer shoe for mounting on
a casing string, comprising a body upon which are arranged
a plurality of reaming members, wherein the reamer shoe is
substantially constructed from a relatively soft drillable
material, wherein the reamer shoe includes a rupture member
which permits increased fluid flow from an interior of the
reamer shoe to the exterior of the reamer shoe, the
plurality of reaming members are movable between a first
and second position, the reaming members are closed in a
first position and expanded in a second position, the
reaming members are operable in the second position to
remove a portion of a wellbore, and each of the reaming
CA 02407506 2006-04-28
7e
members has a hardened material applied to an outer
surface, wherein the reamer shoe includes a rupture member
which permits increased fluid flow from an interior of the
reamer shoe to the exterior of the reamer shoe.
According to an aspect of the present invention there is
provided an expandable reamer shoe substantially
constructed from a relatively soft drillable material, for
mounting on a casing string, the shoe comprising a body
upon which are arranged a plurality of reaming members, an
activating piston within the body, wherein the plurality of
reaming members are moveable between a first and second
position by the action of the piston, the reaming members
being closed in the first position and expanded in the
second position, and a plurality of ramps located
externally to the activating piston, wherein the ramps are
restricted to move within slots formed in the body and
engage the reaming members during movement of the
activating piston.
According to another aspect of the present invention there
is provided a method of inserting an expandable casing into
a borehole using an expandable reamer shoe as previously
described herein, the method comprising the steps of (a)
running a first section of the expandable casing into a
pre-drilled borehole, (b) expanding the first section of
the expandable casing in place, (c) underreaming under the
in-place first section of expanded casing using a standard
underreamer and bit, (d) running a second section of the
expandable casing through the first section of expandable
casing with the expandable reamer shoe, (e) expanding the
expandable reamer shoe, and (f) reaming down the borehole
by rotation or by reciprocation or by both rotation and
CA 02407506 2006-04-28
7f
reciprocation of the expandable reamer shoe to an expected
size.
In order to provide a better understanding of the
invention, an example first embodiment of the invention
will now be illustrated with reference to the following
Figures in which;
CA 02407506 2005-05-02
8
1 Figure 1 illustrates a'cross sectional view of an
2 expandable reamer shoe in accordance with the present
3 invention,
4 Figure 2. illustrates an external view of an expandable
reamer shoe,
6 Figure 3 and 4 illustrate embodiments of the grooves
7 which co-operate with the split ring of the activating
8 piston,- in an alternative cross sectional view expandable
9 reamer shoe,
Figure 5 illustrates:the nose of an expandable reamer
11 shoe with a float valve included,
12 Figures 6 and 7 illustrate alternative retainer rings for
13 use with of an expandable reamer shoe,
14 Figure 8 is a cross sectional view of an alternative
second embodiment of an expandable reamer shoe,
16 Figure 9-and 10 illustrate the nose of the expandable
17 reamer shoe of Figure 8 with a float valve option, and;
18 Figures 11 and 12 illustrate an alternative cross
19 sectional view of the expandable reamer shoe of Figure 8.
21 Referring firstly to Figure 1, an expandable reamer shoe
22 which can'drift and ream a drilled.section of well bore
23 is generally depicted at 1 and is comprised of a
24 cylindrical body (2) with an eccentric nose with ledge
riding capability (3). The body (2) contains an
26 activating piston (4) which is moveable and which defines
27 an internal bore (5). The activating piston (4) has a
28 split ring (6a) which is fitted onto the outside diameter
29 of the piston (4). The body (2) is made from steel and
has hard facing.reaming members (6) which can be seen in
31 Figure 2 applied to the leading end for reaming the inner
32 most section of the drilled hole.
CA 02407506 2005-05-02
9
1 Upon assembly of the tool (1), the activating piston (4)
2 with the split ring (6a) mounted thereon will be inserted
3 into the bore (5) of the body (2). Simple service
4 tooling is used to install the split ring (6a)into the
bore (5) of the body (2). The piston (4) would be slid
6 down to the position shown on the lower side of the
7 centre line of Figure 1. A plurality of ramp segments
8 (7) would then.be welded onto the outside of the piston
9 (4) through slots (8) in the wall of the body (2). The
slots (8) can be seen in more detail on the external view
11 of the reamer shoe (1) seen on Figure 2.
12
13 It can be seen from Figures 3 and 4 that the piston (4)
14 has six slots for the location of six ramp sections (7)
each of which corresponds with one of six external blades
16 (10). When the tool (1) is to be used as a reamer, the
17 blades (10) have hard facing.pre-applied, for.example,
18 hard or super hard metal or diamond. However when.the
19 tool (2) is to be used solely as a drift, the blades (10)
will not need to have cutting grade hard facing. The
21 piston (4), split ring (6a) -and ramp segments (7) are all
22 made from a drillable material such as aluminium alloy.-
23 The blades (10) and body (2) are made from an material of
24 medium hardness; such as alloy steel.
26 A deformable ball or dart (11) is then be dropped into
27 the bore (5) of the piston (4). The ball or dart (11),
28 which would typically be a rubber/plastic or.
29 rubber/plastic coated ball can be seen on the lower side
30. of the centre line-on Figure 1. A retainer ring (12) -is
31 then screwed into place, the retainer ring (12) also
32 being made from a drillable material, such as aluminium.
33 alloy. The retainer ring (12) has holes (13) which allow
CA 02407506 2005-05-09
1 fluid and mud to pass through the retainer'ring (12). when
2 tripping the shoe (1) to the bottom of the well bore.
3 The eccentric nose (3) of the tool (1) may have hard
4 facing (6) applied on the outside and may also have a
5 float valve (14), as seen in Figure 5. The eccentric
6 nose (3) also has a bore which is large enough to
7 accommodate the ball (11) and is typically off-centre to
8 ensure that any subsequent drill bit (not shown) to be
9 passed through the tool (1) can drill through the ball.
10 This prevents the ball (11) from acting as a bearing upon
11 which the drill bit will spin on.
12
13 The assembly (1) can then be fitted onto the end of an
14 expandable casing (not shown) and run into.a pre-drilled
well bore to the end of the section of well bore which
16 has already been drilled and cased. At the end of the
17 existing casing string, the tool (1) is activated just
18 after the new casing enters the new drilled hole section,
19 ie with the tool (1) in the rat hole below the existing
casing. This is achieved by applying power to mud pumps
21. (not shown), attached at the surface and to the top-of
22 the pipe used for running the expandable casing. The
23 flow of mud in the-first few seconds seats the ball (11)
24 into the piston (4), if it is not already in this
location. By applying static pressure thereafter, the
26 ball (11) will seal off the piston bore (5) and pressure
27. will be applied across the full area of the external seal
28 on the piston (4). Thus the piston (4) is encouraged to
29 move down the bore (5) of the body (2) of the tool and in
30doing so deforms the plurality of blades (10) outwards,
31 by virtue of each of the blades (10) communicating with
32 its corresponding ramp segment(7). When the piston (4)
33 is moved down the bore (5) to the body (2), the ball (11)
CA 02407506 2005-05-02
11
1 will rest in position in a seat (18) as shown on the
2 upper side of-the centre line in Figure 1. When the ball
3 (11) rests on the seat (18) in the position seen on the
4 upper side of the centre line in Figure 1, the piston (4)
is stationary and the blades (10) are expanded to gauge
6 size. In this position, the split ring(6a) fits into a
7 corresponding groove (15), which prevents the piston (4)
8 from moving. The retainer ring (12) has seals (16) which
9 are external to the retainer ring (12). The retainer
10. ring (12) has two seals which fit into grooves (not
11' shown) on the external surface of the retainer ring (12).
12 When the seals (16) on the outside of the retainer ring
13 (12) travel past corresponding holes or ports (17) in the
14 body (2), there is a pressure drop at the surface which
indicates that the blades (14) are at their gauge size.
16
17 By continuing to pump dynamically flowing fluid through
18 the body (2) via the holes (17). to the outside, a.dynamic
19 pressure drop will be created. This will 'normally be
lower than the static head which is required to push the
21 piston (4) to this position. However on increasing the
22 pump flow rate, the dynamic pressure head wil.l be
23 increased to a level above the static pressure head which
24 is required to move the piston (4). As a consequence and
at a pre-determined calculated level, the ball (11) will
26 be pushed through the bore and the seat (18) of the
27 piston (4) upon which the ball sits and into a seat in.
28 the eccentric nose (3). Mud can then flow through the
29 nose (3). Rotation of the string can then take place and
reaming to the bottom can commence.
31
32 Figure 5 illustrates a float valve (14) which can be
33 incorporated into the nose (3) of the tool (1). The
CA 02407506 2005-05-02
12
1 float valve (14.) allows mud and cement to pass through
2 the nose (3) through the nozzles (19) in the nose (3) of
3 the reamer shoe (1)to the bottom of the well, so that it
4 can be displaced between the exterior surface of the
casing and the interior surface of the-well bore, to
6 allow the casing to be cemented in place. However, the
7 float valve (14) also ensures that cement cannot flow
.8 back into the reamer shoe through the nose although there
9 would be some leakage through the pressure relief holes
in the body adjacent to the retainer ring but the
11 diametrical gap between the retainer ring and the body
12 would be very small.
13
14 When reaming is completed, the nose (3), piston (4),
split ring(6a), ball (11) and retainer.ring (12) and
16 inside portion-of the ramp segments.can be'drilled out
17 with the drill bit (not shown), with a gauge diameter
18 slightly smaller than the bore (5) of the body (2). The
19 design of the ramp segments located in the:wall of the
20, body and welded to the piston prevents the piston and
21 retainer ring spinning when being drilled out. The body
22 (2) could also be expanded after drill out, by pushing a
23 pig or plug from above the reamer shoe (1). Note that a
24 =seat for a hydraulic expansion seal dart could also be
located in the reamer shoe including at the*entry to the
26 nose designed in this case so that the ball would still
27 pass by or through it, with the ball seat in the guide
28 end of the nose. .
29
Figure 4 illustrates one embodirnent=of the invention,
31 which allows the blades (10) to be retracted after use,
32 wherein each of the blades (10) is adapted to correspond
33 with a ramp section (7) by a dovetail groove (20). The
CA 02407506 2005-05-02
13
1 retainer ring (12) is provided with a profiled'end which
2 accommodates a retriever pulling tool (not'shown), such
3 as an overshot or spear. The retriever pulling tool can
4 be used to pull the piston (4) back into its original
position, hence pulling the blades (10) back into the
6 body (2). Figure 6 illustrates a retainer ring (12)
7 which is adapted to suit a spear (21). Figure 7
8 illustrates a retainer ring (12) which is adapted with an
9 end to suit an overshot (22). It will be appreciated
that de-latching of the overshot or spear will also be
11 required in the event that it is desirable to pull back
12 the casing-string for any reason after reaming has
13 commenced.
14
The tool (1) is-designed to be welded while being
16 assembled and manufactured, so that the amount of
17 components within the internal bore (5) is minimised, and
18 accordingly there are less internal parts which need to
19 be drilled out for the next section of expandable casing.
21 The advantage of the above described embodiment lies in
22 the fact that it is possible to drill through the
23 expandable reamer shoe (1) after having reamed the
24 expandable casingto the bottom, and following expansion
and cementing of the expandable casing. However, it is
26 also recognised in this invention that the reamer shoe
27 (1) could be designed to act solely as a drift for the
28 drilled hole or as a drift in addition to being a reamer
29 shoe. Where the tool (1) is to be used as a drift, its_
dimensions are slightly smaller than that of the outside
31 diameter of the drilled hole, and the tool will not
32 comprise cutting grade hard facing. It is also
CA 02407506 2005-05-09
14
1 recognised that the tool (1) could also be used with
2 standard casing as opposed to expandable casing.
3
4 An alternative second-embodiment of the reamer shoe is
shown in Figure 8, generally depicted at 23. The shoe
6 (23) is made entirely from steel and is millable as
7 opposed to drillable. The shoe (23) can also be
8 retrieved back to the surface if required. The reamer
9 shoe (23) can also be used with a final casing string,
for example in a section which does not require drill-
11 out.
12
13 The body (24) of the tool has three pockets each of which
14 holds a blade (25) with hard metal or super hard metal or
diamond, or other cutting grade material on the external
16 surface, as showri in Figures 9 and 10. It will be
17 appreciated that the cutting grade material will not be
18 included on the blade (25) if the reamer shoe (23) is to
19 be used as a.drift only. The blades (25) 'are activated
by the flow of fluid through the ports or hozzles (26) in
21 the eccentric nose (27) of the tool (23) which creates a
22 dynamic pressure drop between the inside and outside of
23 . the tool (23). This forces the blades (25) out against
24 leaf springs (28) which are mounted in additional pockets
along the length of the sides of the blades (25). Each
26 blade (25) has a series of blade pistons (29) which are
27 screwed into the base of the pockets of the body (24).
28 The blades (25) are driven out to the gauge diameter by
29 the dynamic pressure drop, against stop blocks (30) which
are located at either end of each of the blades (25).
31 The blades (25) are locked in place by the spring
32 activated blocks (30), and reaming then commences to the
33 bottom of the bore: A means to indicate that the blades
CA 02407506 2005-05-02
1 (25) are at the gauge size could.be achieved by adding a
2 pressure relief valve (not shown). The leaf springs (28)
3 hold the blades (25) into the body (24) when.the tool
4 (23) is tripped into the hole. Figure 9 illustrates a
5 cross section of the body (24) when the blades (25) are
6 closed. Figure 10 illustrates the same cross section of
7 the body (24) when the blades are expanded.
8
9 If the tool (23) is to be used on the final string of
10 casing, the tool can be left in-situ without being
11 drilled out. In addition, a float valve (31) can be
12 fitted to the eccentric nose (27) of the tool (23) to aid
13 cementing. Figure 11 illustrates the float valve
14 wherein the valve is closed thereby obturating the entry
15 of fluid such as cement or mud from the body of the
16 tool into the nose (27). Figure 12 shows the float
17 valve (31) when open, which allows fluid to flow into the
18 nose (27) when reaming. If a float valve (31) is not
19 fitted to the nose (27), the nose (27) can be made
integrally with the body- (24).
21
22 The casing can be retrieved at any time while reaming, by
23 pulling the casing string uphole until the, blades (25)
24 bear against the end of the shoe of the last casing
string., and by applying tension to the string from the
26 surface. This will push the blades (25) into the body
27 (24) by shearing the spring activated blocks (30). A
28 bursting disk (32) may also be incorporated into the body'
29 (24) of the tool to increase the flow area through the
tool for cementing. It is envisaged that a bursting disk
31 (32) will be incorporated into the shoe (23) if the
32 nozzles (26) of the nose (27) are small. Incorporation
33 of the bursting disk will ensure that a reasonably high
CA 02407506 2002-10-24
WO O1/83932 16 PCT/GBOl/01512
1 cross sectional flow area is available for cement to pass
2 through. When using a burst disk it is likely that the
3 nose will not incorporate a float valve as'the cement
4 could flow back in through the hole after the disc was
burst. In this case the float valve would be fitted
6 above the burst disc location.
7
8 An advantage of the present invention is that the reamer
9 shoe can be expanded prior to the passage of expandable
casing which will ensure that the casing can expand fully
11 to the desired gauge size. A further advantage is that
12 the reamer shoe may be drilled through by a subsequent
13 drill bit or casing drill shoe with the first embodiment
14 design. This allows further sections of a well-bore to
be drilled below the region which has been lined by the
16 expandable casing, without any damage to the drill bit.
17 The expandable reamer shoe can also be advanced into the
18 borehole by reciprocation and/or rotation.
19
Further modifications and improvements may be
21 incorporated without departing from the scope of the
22 invention herein intended.
